Intro to Pharmacology 1

Pharmacology definition

• The study of substances that interact with living systems through chemical processes or forces

  • Binding to regulatory molecules

  • Enhanced or inhibit “normal” body processes

Medical pharmacology definition

The science or study of substances used for prevention, diagnosis, cure or treatment of diseases (drugs)

Toxicology definition

A branch of pharmacology that studies undesirable effects of chemical substances on living systems

To interact chemically with biologic systems, the substance must have appropriate

• Molecular size

• Electrical charge

• Shape

• Atomic composition

Chemical substances that are useful drug products, must also have physiochemical properties to be:

• Transported intact from point of administration to site of action

• Inactivated or eliminated from the body at a rate that is commensurate with reasonable duration of drug action

Best molecular size of a drug

100 Da (Specificity) to 1000 Da (Bioavailability)

Chemical interactions between drugs and targets occur by means of chemical forces:

• Covalent

• Electrostatic

  • Ionic

  • Hydrogen bonds

  • Induced dipoles

• Hydrophobic

Electrostatic forces are

Much more common than covalent bonding

Hydrophobic bonds are weak and may by important to:

• Interactions between highly lipid-soluble drugs with lipids of cell membrane

• Interactions of drugs with internal walls of their protein targets

Drugs that bind to targets via weaker bonds are

More selective than those that bind by strong bonds

Shape of a drug molecule is critical to drug biologic-target interactions

The shape of a drug molecule must be complementary to the target

More than …% of all useful drugs are chiral molecules (exist as enantiomeric pairs)

50%

Enantiomeric pairs

• Usually, one of the pairs may be more potent than its mirror image enantiomer - which in some cases may not have activity at all

  • This shows that the more potent enantiomer has a relative shape that fits more perfectly with the target than the one that is less potent or inactive

  • Same phenomena is true about drug metabolism (half-life) since enzymes are also stereospecific